High frequency apparatus



1937- P. P. MUSKET ET AL. 2,071,551

HIGH FREQUENCY APPARATUS Filed Aug. 22, 1933 4 Sheets-Sheet 1 Feb. 23,1937. MusKE-r Er AL 2,071,561

HIGH FREQUENCY APPARATUS Filed Aug. 22, 1933 4 Sheets-Sheet 2 1937- P.P. MUSKET ET AL HIGH FREQUENCY APPARATUS Filed Aug. 22, 1933 4Shuts-Sheet 4 Patented Feb. 23, 1937 UNITED STATES PATENT OFFICE HIGHFREQUENCY APPARATUS Application August 22, 1.33, Serial No. 686,237

4 Claims. (Cl- 171-242) More particularly the invention relates to ahigh frequency apparatus for therapeutic and surgical purposes.

It is the general object of the invention to provide a new and improvedhigh frequency apparatus which is stable in operation and may be readilycontrolled.

Another object is to provide such an apparatus embodying a patient'scircuit provided with inductive control.

Another object is to provide such a high frequency apparatus with asimple and readily operable control, a single variable inductance beingprovided in the patients circuit for tuning the circuit.

Another object is to provide a new and improved control means embodyinga variable inductance having a coil and a movable contact, and means forreducing the voltage in the turns being commute-ted.

In pursuance of the foregoing objects the invention, in the form chosenfor purposes of disclosure, is embodied in a high frequency apparatusparticularly adapted for diathermy treatments, and other therapeutic andsurgical purposes.

Other objects will become readily apparent from the following detaileddescription taken in connection with the accompanying drawings, inwhich:

Fig. 1 is a front elevation of an apparatus in which a preferred form ofthe invention is incorporated, illustrating the control panel andcabinet. I

Fig. 2 is a plan view of the oscillator of the apparatus of Fig. 1,viewed from the rear, mounted on the top shelf in the cabinet.

Fig. 3 is an end elevation of the oscillator looking at the right-handend of Fig. 2.

Fig. 4 is an enlarged fragmentary section through the inductive controlmeans.

Fig. 5 is a fragmentary section along the line 6-8 of Fig. 4.

Fig. 6 is a circuit diagram.

While the invention is susceptible of embodiment in many differentforms, we have shown in the drawings and shall herein describe in detailone such embodiment, with the understanding that the present disclosureis to be considered as an exemplification of the principles of theinvention and is not intended to limit the invention to the embodimentillustrated. The scope of the invention will be pointed out in theappended claims.

In the preferred form illustrated in the drawings, the invention isembodied in an apparatus arranged to produce upwards of ten millioncycles in the patient's circuit. This apparatus is enclosed in a cabinet2|) (Fig. 1) and comprises generally a high frequency oscillator (Figs.2 and 3), indicated by a bracket a in Fig. 6, rectifying andtransforming apparatus, indicated by a bracket b in Fig. 6, and apatlent's circuit indicated by a bracket 0 in Fig. 6. The parts arepreferably mounted on a frame which is withdrawable as a unit from therear of the cabinet, the frame having a shelf ii on which the oscillatoris mounted, and the rectifying and transforming apparatus on the lowershelves. The manually operable control members and indicating devicesare preferably mounted on a panel 24, which is carried on the frame soas to be withdrawable therewith.

Referring more particularly to Fig. 6, the oscillator and patient'scircuits incorporated in the apparatus will first be described, withreference to the diagrammatic representation. The physical arrangementof the parts will be described more fully hereinafter. The oscillator isillustrated as comprising a pair of vacuum tubes 36 and having filamentsI and f. grids g and g, and plates 9 and 9', respectively. The twofilaments are connected in parallel, and are connected across asecondary Si of a transformer T by leads 3| and 32. The grids areconnected to a grid oscillating circuit by leads 33 and 34, said circuitcomprising an inductance coil Lg, and condensers Ca and Ca connected inseries with each other (preferably having a common plate, as describedmore fully hereinafter), and connected in parallel with said inductancecoil by leads and 36. A grid leak resistance 31 is connected between themidpoint of the coil La and the mid-point of the condensers Ca and Cd.The plates p and p are connected to a plate oscillating circuit by meansof leads 39 and 46, said circuit comprising an inductance coil Lp,connected in parallel with condensers Cp and Cp, (which are connected inseries with each other, preferably by having a common plate), by leads4| and I.

In the preferred form of the invention the grid circuit condensers Caand Co have a common plate which is formed integrally with a commonplate 45 of the plate circuit condensers Cp and Co. The common condenserplate may be grounded in some instances, By-pass condensers 46 and 46'are herein connected between the filament leads and the condenser plate45, 45'. If desired, a pilot lamp l'l, shunted by a by-pass condenser48, may be connected across the filament supply leads 3| and 32 by leads49 and 50. The oscillator'is connected tothe rectifying and transformingapparatus by means including leads and 52, these leads having highfrequency choke coils 53 and 54 therein, respectively.

The patients circuit 0, as illustrated in Fig. 6, has a capacitycoupling 55 with the plate oscillating circuit of the oscillator, andhas a variable inductance 56 for tuning the circuit and therebyadjusting the current therein. The variable inductance is shown in theform of a coil 51 provided with a movable contact 58, a lead 59connecting one end of the coil to the capacity coupling and a lead 60connecting the movable contact 58 to a patients terminal E. A two scaleload milli-ammeter MA is preferably included in the patents circuit, themilliammeter having a common terminal connected to the capacity couplingby a lead 6I, and low and high scale terminals connected respectively topatients terminals E and E" by leads 62 and 63. Preferably the lead 62has a fuse 65 therein. Thus by connecting electrodes to the patientsterminals E and E the low scale of the milli-ammeter would be in use,and by connecting electrodes to the terminals E and E the high scalewould be in use. The terminals E, E and E may be in the form of sockets,as shown in Fig. l, to permit suitable electrode leads (not shown) to beconnected detachably thereto. Preferably a fixed condenser 64 isconnected in the patients circuit in parallel with the capacity coupling55. This condenser provides a basic capacitance such that whenelectrodes, having the largest capacity commonly encoun tered intreatment, are employed, the patient circuit may be tuned with thevariable inductance near zero. By the use of such a condenser thepatient circuit is rendered very stable and highly efficient because ofthe reduced losses in the inductance. The condenser 64 is preferably amica condenser in order that it may have a large capacity withoutattaining undue bulk.

The oscillator, as illustrated in the drawings, and particularly inFigs, 2 and 3, is of simple and efflcient construction. As will bereadily apparent from these views, the elements of the grid and plateoscillating circuits are symmetrically arranged so as to eliminate to alarge extent the need for separate leads between the parts and minimizesthe length of leads, where leads are provided, and minimizes andbalances leakage capacity. The tubes 30 and 30 are spaced laterally andmounted in vertical positions so that the grid leads or and gr extendfrom the top thereof, and the plate leads pa: and pr extend fromcorresponding projecting side portions of the tubes. The tubes aredetachably mounted in suitable sockets 68 on the supporting shelf 2|.The common plate 45, 45 of the grid and plate circuit condensers extendscentrally between the tubes, as shown most clearly in Fig. 2. This platecooperates with a pair of condenser plates 18 and positioned parallel toand adjacent the right-hand end of plate 45 (Fig. 2) to form the pair ofgrid circuit condensers Cg, Cg (Fig. 6), which are thus connected inseries. The grid leads ya: and gx' are connected directly to posts H and1| (Fig. 3) on the plates 10 and 10'. The grid circuit inductance coilLg is mounted on a pair of insulators 12 by means of L-shaped members 13and screw and nut devices 13', and is positioned above the grid circuitcondensers so as to extend transversely over the condensers. The ends ofthe coil are connected to the condenser plates 10 and 10 by means ofshort connections 14. The grid leak resistor 31 is positioned verticallyat the end of the shelf in substantially the plane of the commoncondenser plate 45 and is connected at one end by a short lead to theplate 45, and at its other end by a short lead 16 to a central point onthe-coil.

The plate oscillating or tank circuit condensers C50 and Cp have plates80 and 80' positioned on the opposite sides of and adjacent the commonplate 45" (Fig. 2), so that said condensers are in effect connected inseries. The plate leads par and ms are connected directly to thesecondenser plates. The inductance coil Lp is mounted on the upper ends ofinsulators 8| by means of L-shaped members 82 and screw and nut devices83, and has its ends connected by short connections 84 to the condenserplates 80 and 60' respectively.

The capacity coupling between the patients circuit and the plateoscillating circuit of the oscillator, as illustrated most clearly inFigs. 2, 3, and 6, includes a pair of plates 90 and 90' which arepositioned parallel to the common condenser plate 45' and intermediatethe lefthand end of this plate (Fig. 2), and the adjacent condenserplates 80 and 80. The plate 98 is connected by means of the lead 59 toone end of the variable inductance coil 51, whereas the plate 90 isconnected by means of the lead 6I to the common terminal of themilliammeter MA. The condenser 64 (Fig. 6) connected in parallel withthe patients circuit, is shown as comprising portions of the plates 90and 90' (Fig. 2), a pair of plates 9| and M and an intermediate plate93, the plates being separated by sheets of mica or other suitabledielectric 92, 92' and 94, 94'. The plates 9| and 9| are preferablyformed integrally with a connecting portion 9|". As illustrated hereinthe plates 90 and 90' together with the other parts of condenser 64 aremounted as a unit directly upon the shelf 2| by means of a. plurality ofL-shaped members 95, and are thereby supported independently of theplate oscillating circuit elements.

The inductance coil 51, which is herein provided in the patients circuitfor the purpose of varying the current and tuning the circuit, ismounted in a horizontal position on the back of the panel 24 (Figs. 2,3, and 4) by means 01 end brackets I60, which also carry a pair of sliderods I6I extending longitudinally of the coil. Preferably a pair ofsliding contacts 58 are provided, these contacts being operable by meansincluding a knurled knob I62 positioned in front of the control panel24. The knob I62 is non-rotatably secured to a shaft I63, the shaftbeing rotatably mounted in a bracket I64 which is suspended from the endbrackets I66 by means of bars I64. A gear wheel I65 is secured to theshaft and meshes with a rack I66 which is slidable longitudinallybeneath the coil. The contacts 58 are secured to a ring or band I61 bymeans of resilient mounting members I68, the ring I61 being carried on amember I69 which is slidable on the rods I6I. The rack I66 is secured tothe sliding member I69. Thus by rotating the knurled knob I62 thecontacts 58 may be moved over the coil turns.

Preferably the ring I61, as illustrated most clearly in Figs. 2, 4, and5, is of sufficient length so as to overlie a plurality of turns on thecoil 51. This ring is formed of metal and serves as a means for reducingthe voltage in the turns being commutated by the contacts 84 for thepurpose of preventing sparking and pitting of the contacts. The ring, ofcourse, moves with the contacts longitudinally of the coil and providesfor efficient operation of the variable inductance.

The rectifying and transforming apparatus for supplying a pulsatingdirect current to the oscillator through the leads II and '2 will now bedescribed with particular reference to the circuit diagram in Fig. 6. Inthe form illustrated in the drawings. this apparatus comprises aplurality of rectifier tubes I44 and I44 having filaments III and platesI42. The filaments are connected across individual secondary windings 82and 82' on the core Tc of the transformer T, the primary winding P ofwhich is arranged to be excited by 110 volt 60 cycle alternating currentas hereinafter more fully described. The plates "2 of the tubes I areconnected to the opposite ends of the secondary S3 of a transformer T bymeans of leads Ill and I44, and are connected to the mid-points of thesecondary transformer windings 82' by means of leads I" and I. Theplates of the tubes III are connected together by a lead I" and to oneside of a plate current milli-ammeter MA by means of a lead I. The otherterminal of the milli-ammeter is connected to the mid-point of thetransformer secondary Si by means of leads I and H0. The mid-points ofthe transformer secondaries B2 are connected together by leads III andH2 and to one side of a condenser III by a lead H4. The other side ofthe condenser H2 is connected by a lead III to the iunction of the leadsI" and III. The oscillator leads II and '2 may be connected to the leadsI and H4 as illustrated.

The primaries and secondaries of the transformers T and T areproportioned so as to provide the necessary voltages for the filamentsand plates of the various tubes. As mentioned hereinbefore the primary Pof the transformer T, in the preferred form of the invention, is adaptedfor connection to a 110 volt 60 cycle alternating current supply. Thisis also true with respect to the primary P of the transformer T. Thetransformer primary P, as illustrated in Fig. 6, has one end connectedby means of a lead I24 to one end of a resistor I2I of a filamentrheostat FR. a movable contact I22 of the rheostat being connected by alead I24 to one terminal I24 of a filament control switch FC. The otherterminal I24 of the switch FC is connected to one end of a highfrequency choke coil HFC, the other end of the choke coil beingconnected to a line terminal I28. The other end of the transformerprimary P is connected by leads I2! and I26 to a similar high frequencychoke coil HFC', the other end of which is connected through a suitablefuse I21 to a second line terminal I24. A volt meter V is preferablyconnected across the transformer primary by leads III and I32.

In order to insure proper heating of the rectifier tube filaments priorto the energization of the plate circuits, one end of the primary P ofthe transformer T is connected to a time delay switch TDS by a lead I".The time delay switch may be of any preferred form and preferablyembodies a heating element operable when current first flows in theprimary circuit of the transformer T so that there will be a definitelapse of time after the filament current switchI'CisclosedbeforetheprimaryP'isexcited. The

other end of the primary P is connected to one side of a circuit breakerCB by a lead I40, the other side of the circuit breaker being connectedby a lead I to one end of an adjustable impedance coil I42. A movablecontact I43 is connected by a lead I44 to one terminal I45 of a platecurrent switch PC, the other terminal I4. of which is connected to oneside of the filament current switch FC by a lead I41. Preferably aresistor I44 is shunted across the circuit breaker CB so that if thecurrent in the plate circuit exceeds a predetermined value the circuitbreaker, upon opening, will automatically insert the resistor I4. in thecircuit so as to limit the current. (The circuit breaker may be closedby a handle CB, Fig. 1). It will be apparent that the current to theprimary P also passes through the filament current switch PC so that itis necessary first to close the filament current switch. However, thetime delay switch is also included to delay properly the excitation ofthe rectifier tube plates. For convenience in operation, a foot operatedswitch I" is connected in parallel with the plate current switch PC.

when used for diathermy treatments, condenser type electrodes arepreferably used, i. e., electrodes spaced from the patient by a suitabledielectric. The electrode leads are connected to the terminals E and Eif it is desired to use th low scale of the load milli-ammeter, and areconnected to the terminals E and E" if it is desired to use the highscale of the meter. If low currents are being used the circuit breakerCB may be left open. the circuit breaker being generally closed whenrelatively high currents are used so that if there should be a markedincrease in current above the value at which the controls are originallyset, the breaker will open and insert the resistance I42 in the platecircuit. After the electrodes have been connected and properly adjustedto a patient. the filament current switch PC is closed and the voltageacross the primary P of the transformer T properly adjusted by means ofa knurled knob I (Fig. 1) which is operable to adjust the contact I22(Fig. 6) of the filament rheostat FR. After sufiicient time has elapsedto permit the filaments to heat properly the plate circuit of therectifier may be closed either by means of the switch PC or the footoperated switch. I50. In Fig. 1 there is shown one part Iii of adetachable connecter secured to the panel 24, this part having itscontacts suitably connected in parallel with the terminals of the switchPC. The other part of the connecter (not shown) may have suitableflexible leads connected to a foot switch so as to enable the operatorto close and open the plate circuit of the rectifier by means of hisfoot if this is found more convenient. Should the plate circuit beclosed before sufilcient time has elapsed the time delay switch TDSfunctions to hold the plate circuit open for the requisite period. Assoon as the plate circuit is closed the oscillator will commence tooperate after which the patient's circuit may be tuned by means of thevariable inductance 56, the operator manipulating the knurled knob I62for this purpose. The variable impedance I42, I43 may be adjusted forchanging the current, a knurled knob I52 being mounted on the front ofthe panel 24 (Fig. 1) for this purpose.

We claim as our invention:

1. A variable inductance comprising, in combination, a coil. a contactmovable longitudinally of the coil and in engagement with the turnsthereof, and means for reducing the voltage across the turns of the coilbeing engaged by said contact, said means comprising a metal ringsurrounding the coil in spaced relation thereto and movablelongitudinally thereof with said contact and overlying a plurality ofturns of the coil, said contact being carried within said ring.

2. A variable inductance comprising, in combination, a coil, a contactmovable longitudinally of the coil and in engagement with the turnsthereof, and means movable with the contact for inductively reducing thevoltage across the turns of the coil being engaged by said contact.

3. A variable inductance comprising, in combination, a coil, a metalring surrounding the coil overlying a plurality of turns of the coil andmovable longitudinally thereof, and a plurality of circumferentiallyspaced contact members carried within said ring and in engagement withthe turns of the coil.

4. A variable inductance comprising, in combination, a coil having aplurality of turns spaced longitudinally thereof, a metallic ringsurrounding the coil and having contact with the turns thereof, saidring overlying a plurality of turns of the coil, and means supportingsaid ring for sliding movement longitudinally of the coil.

PETER P. MUSKET. DONALD E. RICHARDSON.

